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DS3232M

Alarms

The device contains two time-of-day/date alarms.

Alarm 1 can be set by writing to registers 07h–0Ah.

Alarm 2 can be set by writing to registers 0Bh–0Dh.

See Table 2. The alarms can be programmed (by the

alarm enable and INTCN bits in the Control register)

to activate the INT/SQW output on an alarm match

condition. Bit 7 of each of the time-of-day/date alarm

registers are mask bits (Table 2). When all the mask

bits for each alarm are logic 0, an alarm only occurs

when the values in the timekeeping registers match the

corresponding values stored in the time-of-day/date

alarm registers. The alarms can also be programmed

to repeat every second, minute, hour, day, or date.

Table 3 shows the possible settings. Configurations

not listed in the table result in illogical operation. The

DY/DT bits (bit 6 of the alarm day/date registers) con-

trol whether the alarm value stored in bits 0–5 of that

register reflects the day of the week or the date of the

month. If DY/DT is written to logic 0, the alarm is the

result of a match with date of the month. If DY/DT is

written to logic 1, the alarm is the result of a match

with day of the week. When the RTC register values

match alarm register settings, the corresponding alarm

flag A1F or A2F bit is set to logic 1. If the correspond-

ing alarm interrupt enable A1IE or A2IE bit is also set

to logic 1, the alarm condition activates the INT/SQW

signal if the INTCN bit is set to logic 1. The match is

tested on the once-per-second update of the time and

date registers.

Table 3. Alarm Mask Bits

DY/DT

ALARM 1 REGISTER MASK BITS (BIT 7)

ALARM RATE

A1M4

A1M3

A1M2

A1M1

X

1

1

1

1

Alarm once a second

X

1

1

1

0

Alarm when seconds match

X

1

1

0

0

Alarm when minutes and seconds match

X

1

0

0

0

Alarm when hours, minutes, and seconds match

0

0

0

0

0

Alarm when date, hours, minutes, and seconds match

1

0

0

0

0

Alarm when day, hours, minutes, and seconds match

DY/DT

ALARM 2 REGISTER MASK BITS (BIT 7)

ALARM RATE

A2M4

A2M3

A2M2

X

1

1

1

Alarm once per minute (00 seconds of every minute)

X

1

1

0

Alarm when minutes match

X

1

0

0

Alarm when hours and minutes match

0

0

0

0

Alarm when date, hours, and minutes match

1

0

0

0

Alarm when day, hours, and minutes match